Spray apparatus



p 7, 1966 R. L. PEASLEE ETAL 3,275,240

SPRAY APPARATUS 2 Sheets-Sheet 1 Filed Jan. 5, 1964 45 INVENTORS.

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SPRAY APPARATUS Filed Jan. 5, 1964 2 Sheets-Sheet a /02 W /6- K M am 5% 25 /fiz5 Ma 95 M 34v /.90 3 66 ,12 g Fig.4.

United States Patent M 3,275,240 SPRAY APPARATUS Robert L. Peaslee, Royal Oak, and Clifford C. Tennenhouse, Southfield, Mich., assignors to Wall Colmonoy Corporation, Detroit, Mich., a corporation of Delaware Filed Jan. 3, 1964, Ser. No. 335,502 3 Claims. (Cl. 239-61) The present invention broadly relates to spray apparatus of the type for forming a composite spray including gas propelled atomized liquid globules and solid powder particles, and more particularly to an improved spray apparatus adapted for concurrently applying a liquid binder and fine-sized metallic powder particles on a metallic surface which on subsequent heating effects disintegration of the binder and fusion of the powder particles forming an adherent metallic surface coating on the substrate.

Various techniques have heretofore been used or proposed for use for applying high-temperature wear and/ or corrosion resistant metallic coatings on the surface of a metal substrate. One technique which has been found eminently satisfactory in principle comprises the deposition of a layer of fine-sized metallic particles of a suitable abrasion and/ or corrosion resistance alloy on the surface of a metallic substrate followed thereafter by fusion of the powder at an elevated temperature forming a continuous adherent metallic surface coating. It has been found necessary in most instances to employ a suitable liquid binder for temporarily adhering the metallic powder on the surface of the metallic substrate to prevent inadvertent dislodgement thereof prior to the fusion of the powder particles at an elevated temperature. During the fusion operation, the binder either volatizes or thermally decomposes so as not to interfere with the adherence of the fused metallic powder particles on the surface of the substrate.

One technique heretofore employed for applying a metallic powder coating on a surface of a metal object to be coated comprises the formation of a liquid slurry consisting of the metallic powder and a liquid binding agent which is sprayed on the surface of the metal substrate employing a conventional spray gun. This technique, however, is extremely ineflicient, costly and produces problems due to the necessity of maintaining the slurry under continuous agitation to prevent segregation or stratification of the metallic powder particles in the liquid'binder. In spite of relatively elaborate agitation systems, stratification of the powder particles in the binder has occurred resulting in the application of substantially clear binder or alternatively a slurry having an excessive loading of powder particles therein resulting in large variations in the amount and uniformity of metal powder on the surface of the object being coated. Additionally, a fouling and plugging of the fine-sized orifices and passageways of the spray apparatus frequently occurs as a result of the attempted spraying of stratified slurries having portions which are excessively high in powder content. The fouling or plugging of the spray apparatus necessitates a tedious and time consuming cleaning to restore it to proper operating condition which seriously detracts from the efficiency and economy of its use.

Slurry spray equipment of the aforementioned type has the further disadvantage of requiring relatively expensive and complex agitation and mixing equipment in addition to requiring the blending of a relatively large size batch of the material to provide satisfactory operation. Frequently a substantial portion of the slurry batch is not used during short production runs necessitating either continuous agitation to maintain the slurry of homo- Patented Sept. 27, 1966 geneous consistency during the interim period or encountering a great deal of difliculty in effecting even distribution of the settled metallic powders in the liquid binder after the slurry has settled while standing over a long period of time. This technique further requires the maintenance of relatively large inventories of powder which in the case of so-called super alloys which are of relatively high cost, constitutes a considerable capital investment.

Alternative techniques heretofore used or proposed which are subject to many of the disadvantages heretofore set forth include the formation of a slurry of a liquid binder and metal powder which is applied to the parts by either dipping or by brushing. While the dipping or brushing of the slurry overcomes problems in the servicing and cleaning of the spraying equipment, it is difficult to control the thickness of the coating and the uniformity of its distribution which further detracts from the utility of these techniques.

It will be apparent from. the foregoing that there has been a long felt heretofore unfilled need for providing a method of depositing a substantially uniform or a 'controlled nonuniform coating comprising a plurality of finesized metallic particles on all or a portion of a metal surface which is retained thereon by a suitable binding agent prior to furnace fusion in which the binding agent either volatizes or thermally decomposes and the metallic particles melt and fuse forming an adherent smooth surface coating. It is accordingly a principal object of the present invention to provide an improved spray apparatus for applying a liquid binder and a finely-particulated solid powder on the surface of a substrate which fulfills a long-felt need and overcomes the disadvantages inherent in apparatuses and techniques heretofore known.

Another object of the present invention is to provide an improved spray apparatus wherein the finely-particulated powder and the liquid binding agent are maintained separated until a controlled portion of the powder is injected into and entrained by a gas-propelled spray containing atomized globules of the liquid binder as it is directed toward the surface of an article to be coated.

Still another object of the present invention is to provide an improved spray apparatus incorporating means therein providing for a preselected delay in the introduction of the solid powder into the spray consisting of gaspropelled liquid .bin-der globules assuring an initial coating of the surface with binder thereby preventing a bouncing off or lack of adherence of the initial charge of powder particles impinging on the surface to be coated.

A further object of the present invention is to provide an improved spray apparatus incorporating a pneumatic control system for effecting the formation of a composite spray pattern including minute globules of liquid binder and solid powder particles which is devoid of any electrical components that might present a fire hazard when spraying binder compositions employing volatile flammable solvents.

A still further object of the present invention is to provide an improved spray apparatus which enables the coating of plane as well as irregularly shaped surfaces with a powder layer which can be applied uniformly or alternatively can be built up along selected sections to form heavier layers as may be desired.

Still another object of the present invention is to provide an improved spray apparatus for applying a liquid binder and solid powder particles to a metal surface which is of versatile use, of durable operation, of simple cleaning and maintenance, and of economical manufacture and operation.

The foregoing and other objects and advantages of the present invention are achieved by a spray apparatus comprising a first nozzle for discharging a gas propelled spray of atomized liquid globules and a second nozzle for discharging finely-particulated solid powder particles entrained in a gas stream into the spray from the first nozzle effecting substantially uniform entrainment therein. The discharge of the powder from the second nozzle is effected in response to the flow of a preselected quantity of gas out through the first nozzle as sensed by suitable flow sensing means incorporated in the gas supply line which is operative to open a valve for effecting an aspiration and entrainment of the solid powder and a controlled withdrawal thereof from a storage hopper for discharge through the second nozzle.

"In accordance with this apparatus, the liquid binder and the solid powder are maintained in separated condition until just prior to their mutual entrainment in a spray directed at the surface to be coated avoiding the complexity of the equipment and the problems encountered in the apparatuses and techniques heretofore known.

Other objects, features, and advantages of the present invention will become apparent from the subsequent description, taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a side elevation view of the spray apparatus comprising the present invention illustrating the relationship of each of the operating components thereof;

FIG. 2 is an enlarged vertical sectional view through the spray gun of the apparatus shown in FIG. 1;

FIG. 3 is an elevation view of the front of the spray gun as viewed in FIG. 2 along the lines 33 thereof;

FIG. 4 is a fragmentary vertical sectional view of the orifice and diaphragm valve shown in FIG. 1;

FIG. 5 is a fragmentary side elevation view partly in section of the hopper for containing the solid powder and the aspirator means in the base thereof for effecting a controlled withdrawal of the powder therefrom; and

6 is a fragmentary vertical sectional view of a substrate having a coating of a binding agent and powder particles thereon as provided by the apparatus shown in FIG. 1. 7

Referring now in detail to the drawings and as may be best seen in the FIG. 1, the spray apparatus comprising the present invention consists of a conventional spray gun indicated at 10 of a type well known in the art including a container or tank 12 in which a suitable liquid binder is stored for discharge from the nozzle of the spray gun. The spray gun and its internal construction is shown in greater detail in FIG. 2. The spray gun 10 is connected to a supply system for supplying a pressurized liquid gas such as air for example, to the discharge nozzle of the spray gun and comprises a supply line 14 having a main shutoff valve 16 therein and which is further provided with a water and dirt trap 18 for removing any foreign entrained moisture and dirt from the gas supply. The gas passing from the water trap 18 enters a pressure regulat-or 20 which can be preset so as to provide the desired working pressure to the spray gun for effecting optimum atomization of the .liquid binder and the formation of a spray pattern of the desired velocity consistent with the shape and size of the spray nozzle and the specific shape and size of the object to be coated.

The pressure regulated gas thereafter passes through a T-fitting 22 from which a portion passes through a conduit 24 and into a coupling 26 of a diaphragm valve assembly indicated at 28. The gas passing from the coupling 26 is discharged into a suitable flexible hose 30 which is connected to the lower end of the handle of the spray gun 10.

A second portion of gas is transmitted from the T- fitting 2-2 to an elbow 32 to a second pressure regulator 34 effecting a further controlled reduction in its presvalve 54 in a manner well known in the art.

sure and thence to the inlet side of a valve body 36 of the diaphragm valve assembly 28. Assuming that the diaphragm valve assembly is in open position permitting the passage of the gas through the valve body 36, the gas thereafter passes through a pipe 38 to an aspirator assembly 40 mounted in the base of a container or hopper 42 which contains a charge of the dry particulated solid powder. The aspirator assembly is operative in response to the passage of gas therethrough in a manner sub- .sequently to be described to effect a fluidization and withdrawal of a controlled amount of the powder from the base of the hopper 42 and is carried through a flexible conduit 44 to a second nozzle 46 mounted in front of the nozzle of the spray gun and is formed with an orifice 48 positioned so as to discharge the gas and the entrained powder into the spray pattern emitted from the spray gun.

The specific construction of the several components comprising the spray apparatus as shown in FIG. 1 as well as their operating relationship will now be described in detail commencing with the spray gun as best is seen in FIGS. 2 and 3. It will be understood that the specific construction of the spray gun 10 as shown in FIG. 2 is merely exemplary of a variety of commercially available spray guns which can be satisfactorily employed in accordance with the practice of the present invention. The spray gun 10 as illustrated is of the so-called pistol type incorporating a trigger 50 which on movement in a counter-clockwise direction as viewed in FIG. 2 is operative to actuate a poppet valve 52 and .a fluid needle A typical spray gun of this type is commercially available from Binks Manufacturing Company of Chicago, Illinois, and is designated as model 29.

The spray gun as illustrated is of the siphon type employing an external mix nozzle whereupon the liquid binder is withdrawn from the container or tank 12 upwardly through a vertical passageway 56 and thence out through a horizontal passageway 58 which terminates at its forward end in a circular orifice or nozzle 60 in which the conical end of the fluid needle valve '54 is seated. The gas discharged from the spray gun passes upwardly through apassageway 62 in the handle of a gun which is disposed in communication with an annular passageway 64.which in turn is disposed in communication with a chamber 66 comprising the high-pressure side of the poppet valve 52. In response to movement of the trigger 50 the poppet valve 52 is unseated enabling pressurized gas to pass from the chamber '66 through a passageway 68 to an annular passageway 70 which is disposed in communication with a series of longitudinally extending ports 72 in the body of the fluid nozzle. The pressurized gas discharge from the ports 72 passes outwardly through an annular nozzle 74 encircling the fluid nozzle or orifice 60 applying suction and withdrawing liquid binder from the horizontal passageway 58 in response to the rearward withdrawal of the fluid needle valve 54. The amount of liquid binder in the spray is controlled by the adjustment of degree of opening of the fluid needle valve 54. The high velocity of the gas passing from the annular nozzle 74 effects fragmentation and atomization of the liquid binder withdrawn through the fluid orifice 60 effecting external mixing and the formation of a gas propelled spray of minute liquid globules.

The atomized gas-propelled spray from the annular nozzle 74 and the fluid nozzle 60 is in the form of a cone and can be varied to any desired fan shape by controlling the discharge of air from a pair of diametrically disposed angularly aligned jets 76 in a pair of lugs 78 formed integrally with the air nozzle cap 80. The second nozzle 46 for discharging the fluidized powder is conveniently mounted and secured to the lugs 78 in a manner as may be best seen in FIGS. 2 and 3. As will be noted in FIG. 2 the orifice 48 in the second nozzle 46 is angularly inclined forwardly for discharging the solid powder directly into the path of the gas propelled spray containing globules of the liquid binder.

It will be understood that in lieu of employing a siphontype external mix nozzle arrangement in the spray gun as illustrated in FIGS. 2 and 3, satisfactory operation can also be obtained by employing a pressure-type external mix nozzle wherein the liquid binder is fed under pressure to the nozzle. The pressure may be developed such as for example by a pressure tank or any one of a variety of suitable pumps for feeding the liquid binder to the nozzle. Similarly an internal mix-type nozzle can be employed wherein atomization of the liquid binder is achieved by mixing the air and liquid within the air nozzle and thereafter the material is sprayed from the head of the gun through an orifice the shape of which determines the shape of the pattern. It has been found for the purposes of the present invention that an external mix-type nozzle is preferred to which the liquid binder is fed either through a siphon action or a pressure-feed arrangement.

The pressurized gas for actuating and torming the spray pattern which conventionally comprises air is supplied from the supply line 14 connected to a suitable highpressure source and is reduced by the pressure regulator to within a range appropriate for achieving operation of the spray gun consistent with consideration of the specific size of the nozzle orifices therein as well as the viscosity of the liquid binder being sprayed. Conventionally operating pressures in a range of from about 30 to about 60 p.s.i. are suitable while a pressure of about 50 p.s.i. is recommended for the spray gun shown in the drawings. On the initiation of the spray cycle the poppet valve 52 is first opened in response to the movement of the trigger 50 effecting a flow of gas or air to the coupling 26 and then through the flexible hose 30 for discharge out through the air nozzle. The quantity of air discharged from the nozzle of the spray gun is controlled by the opening position of the poppet valve 52 in accordance with the angular deflection of the trigger 50. A threshold volume or quantity of air is required depending on the specific size and configuration of the air nozzle and the viscosity of the liquid binder siphoned from the container 12 to provide a satisfactory spray pattern. The system in accordance with the present invention incorporates automatic means for withholding the discharge'of the solid powder until the flow rate of air discharged from the spray gun is of a magnitude sufiicient to provide a satisfactory spray pattern containing the atomized globules of liquid binder therein.

This is achieved in accordance with the present invention by the provision of the diaphragm valve assembly 28 including the coupling 26 as best seen in FIG. 4 which is formed with an inlet port 82 and an outlet port 84 separated by an orifice or restriction 86 the cross-sectional area of which is adjustable by means of a set screw 88 having a shank end adapted to project a preselected distance into the orifice 86. In accordance with this atrangement, a preselected pressure drop occurs across the orifice 86 in response to the passage of gas to the spray gun. The differential pressure between the inlet port 82 and the outlet port 84 increases as the flow rate of gas increases. The inlet port 82 is connected by means of a conduit 90 to one side of a housing 92 and the outlet port 84 is connected by :a conduit 94 to the opposite side of the housing 92 which is internally divided by means of a flexible diaphragm 96 in two chambers.

A rod or valve stem 98 is afiixed at one of its ends to the diaphragm 96 and is slidably disposed in guided relationship in a bore 100 formed in an extension 102 of the housing 92. A resilient valve 104 is affixed to the opposite end of the valve stem 98 and is resiliently biased by means of a coil spring 106 disposed against the diaphragm 96 toward gas-tight sealing engagement against a valve seat 108 formed in the interior of the valve body 36. The valve seat 108 is disposed between an inlet and propelling most finely particulated powders.

6 port 110 and an outlet port 112 of the valve body 36 through which gas is passed through the pipe 38 and into the aspirator assembly at the base of the hopper 42 (FIG. 1).

It will be apparent from the arrangement of the diaphragm valve assembly 28 as shown in FIG. 4 that in the absence of any flow of gas through the coupling 26, or under conditions where only a relatively low volume of gas moves through the orifice or restriction 86 therein only a minor pressure diiferential exists between the inlet port 82 and the outlet port 84 and correspondingly only a small pressure differential exists on opposite sides of the diaphragm 96 such that the coil spring 106 maintains the valve 104 in firm seating relationship against the valve seat 108 preventing passage of gas therethrough to the aspirator assembly 40. Under such condition where the flow rate of gas through the orifice 86 attains a preselected magnitude corresponding to one at which an adequate atomized spray pattern of liquid binder globules is discharged from the head of the spray gun, and increased pressure differential occurs which is sufficient to overcome the resilient biasing force of the coil spring 106 effecting movement of the diaphragm toward the low pressure side or to the left as. viewed in FIG. 4 effecting an opening of the valve 104 away from the valve seat 108. Accordingly, gas is now permitted to pass to the aspirator assembly 40 effecting fluidization and discharge of solid powder from the orifice 48 in the second nozzle 46.

The opening of the valve 104 to coincide with the passage of a controlled quantity of gas to the spray gun assuring the presence of an adequate spray pattern can be adjusted by means of the set screw 88 and the resilient biasing force of the coiled spring 106 to prevent the discharge of powder at such other times that an inadequate spray pattern is present. This assures not only that a uniform composite spray of the fine-sized globules of liquid binder and solid powder particles is attained but also provides for a short time delay between the initiation of the application of a binder coating to the surface to be coated before the powder particles are entrained in the spray. This minimizes the likelihood of the powder particles striking a surface which does not have at least a thin film of liquid binder thereon which would otherwise prevent adherence of the powder and a waste of the relatively expensive surface coating or corrosion resistance powder.

The pressure of the air or gas transmitted to the aspiratorassenrbly 40 is controlled by the setting of the pressure regulator 34 and which provided for a further reduction in pressure so as to provide -for optimum fluidization and entrainment of the powder and its discharge while entrained in the gas stream from the orifice 48 in the second nozzle 46. Pressures in the order of about /2 to to that employed for forming the atomized liquid spray have been found satisfactory for fluidizing The pressure to be employed will depend upon such related factors as the size of the solid powder particles, the density of the particles, the specific design of the aspirator assembly 40, and the quantity of powder to be fed into the spray to provide optimum coating characteristics consistent with the specific coating operation to be performed.

Fluidization and entrainment of the powder by the aspirator assembly 40 is achieved in accordance with the construction as shown in FIG. 5 by employing a nozzle 114 through which the inlet gas is discharged and which is positioned in spaced axial alignment relative to a tube 116 having a bore 118 therethrough disposed in communication with a chamber 120 the outlet end of which is adapted to be connected to the flexible conduit 44 connected to the nozzle 46 (FIG. 1). The powder which is contained within the hopper 42 moves downwardly by gravity into a cylindrical chamber 122 of the aspirator assembly 40 in which the nozzle 114 and tube 116 are positioned. The powder surrounds the nozzle 114 and the inlet to the bore 118 in the tube 116 such that upon the discharge of gas from the nozzle 114 the powder in the immediate vicinity of the nozzle is fluidized and is entrained in the gas jet as it passes through the bore 118 into the chamber 120. The gas stream containing entrained powder particles therein is thereafter carried by the flexible conduit 44 to the nozzle 46 and is discharged through the orifice 48 therein to become entrained in the spray emitted from nozzle of the spray gun. A bleed tube 124 is preferably provided in the chamber 122 which is vented to the interior of the hopper 42 to provide for improved fluidization and a more uniform discharge of powder from the nozzle 46.

It will be apparent from the foregoing that the entire system is pneumatically controlled in response to the initiation of discharge of gas or air from the air nozzle in response to the opening of the poppet valve 52 by the trigger 50. The powder particles and the liquid binder are maintained segregated at :all times until the powder is injected into the spray such that at the completion of a spray operation relatively simple cleaning of the equipment can be accomplished. Moreover, by simply changing the type of powder in the hopper 42 which can be drained by removing a cap 126 at the base of the aspirator assembly 40 (FIG. and recharging the hopper 'with a second type of powder quick conversions of the system can be accomplished with a minimum of down-time. Similarly, a switching of tanks or containers 12 containing different types of liquid binder constituents consistent with the nature of the coating to be formed can be quickly achieved further enhancing the flexibility and versatility of the apparatus.

While the spray apparatus as hereinabove described and as shown in the drawings is applicable for the formation of a variety of composite sprays comprising an atomized liquid and a finely-particulated solid powder, the apparatus is particularly satisfactory for applying metallic powders which on subsequent fusion at elevated temperatures accompanied by a vaporization or thermal decomposition of the binder constituents provide for adherent corrosion resistance and/or wear-resistance sur face coatings. For this purpose any one of a variety of liquid binder materials can be employed such as for example .a solution of a thermoplastic resin in an organic solvent including resins such as for example acrylic resins forming lacquers which dry rapidly forming an adherent composite coating of the type illustrated in FIG. 6. The powder particles may comprise any one of a variety of corrosion or wear resistant alloys including nickel base alloys which are comminuted to a particle size in the order of several microns enabling simple fluidization and entrainment thereof in a gas stream. Organic binders employing organic solvents which are relatively volatile facilitate rapid drying of the binder on the substrate effecting firm adherence of the metallic particles therein prior to the subsequent fusion operation at an elevated temperature.

FIGURE 6 illustrates a coating 128 applied on a substrate 130 comprising tenaciously bonded powder particles distributed substantially uniformly therethrough and adhered to the surface.

While it will be apparent that the preferred embodiments herein illustrated are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. A spray apparatus for forming a composite spray of gas-propelled liquid globules and solid particles comprising a first nozzle, supply means for supplying a pressurized gas to said first nozzle, means for supplying a liquid to said first nozzle in a manner to effect atomization thereof and discharge from said first nozzle in the form of a gas-propelled spray of fine-sized liquidglobules, a second nozzle, means for supplying a finely-.particulated solid powder includiug gas-actuated means for fluidizing and discharging said powder at a controlled rate to said second nozzle into said spray from said first nozzle effecting entrainment of said powder in said spray, a conduit connected to said gas-actuated means and to said supply means, an orifice in said supply means, sensing means for sensing the pressure drop across said orifice in response to the flow of gas therethrough to said first nozzle, first valve means in said conduit operatively associated with said sensing means and movable to an open position when a preselected pressure drop is exceeded enabling passage of gas to said gas-actuated means and movable to a closed position preventing passage of gas to said gasactuated means when the pressure drop is below the preselected level, and second valve means for controlling the rate of flow of gas to said first nozzle.

2. A spray apparatus for forming a composite spray of gas-propelled liquid globules and solid particles comprising a first nozzle, supply means for supplying a pressurized gas to said first nozzle, means for supplying a liquid to said first nozzle in a manner to effect atomization thereof and discharged from said first nozzle in the form of a gas-propelled spray of fine-sized liquid globules, a second nozzle, means for supplying a finely-particulated solid powder to said second nozzle including gas actuated aspirator means for fluidizing and discharging said powder at a controlled rate into said spray from said first nozzle effecting entrainment of said powder in said spray, a conduit connected to said aspirator means and to said supply means, differential pressure actuated valve means in said conduit comprising a housing defining an internal chamber, a diaphragm in said chamber dividing said chamber into two compartments, valve means on said diaphragm and movable thereby to and from an open position and a closed position, biasing means for biasing said valve means toward said closed position, an orifice in said supply means for effecting a pressure differential thereacross in response to the flow of gas therethrough to said first nozzle, conduit means disposed in communication with opposite sides of said orifice and to respective ones of said compartment for applying differential pressure across said diaphragm effecting an opening of said valve means in opposition to said biasing means when a preselected differential pressure is exceeded enabling passage of gas to said aspirator means and for preventing flow of gas to said aspirator means when the differential pressure is below the preselected level, and second valve means for controlling the rate of flow of gas from said supply means to said first nozzle.

3. A spray apparatus for forming a composite spray of gas-propelled liquid globules and solid particles comprising a first nozzle, supply means for supplying a pressurized gas to said first nozzle, sensing means for sensing the rate of flow of gas to said first nozzle, means for supplying a liquid to said first nozzle in a manner to effect atomization thereof and discharge from said first nozzle in the form of a gas-propelled spray of fine-sized liquid globules, a container for holding a charge of a finelyparticulated soli-d powder, a gas actuated aspirator in the base of said container including a nozzle for discharging a stream of gas therefrom, a port disposed in spaced axial alignment with said nozzle for receiving the stream of gas therefrom and the entrained powder in said stream, a second nozzle, means connecting said aspirator to said second nozzle for discharging the fluidized powder from said second nozzle into said spray from said first nozzle effecting entrainment of said powder in said spray, a conduit connected to said nozzle of said aspirator and to said supply means, first valve means in said conduit operable to open in response to said sensing means when a preselected rate of flow of gas to said first nozzle is exceeded and for preventing flow of gas to said aspirator when the ate of HO! 0f gas to said first nozzle is below said preselected rate, and second valve means for controlling the rate of flow of gas to said first nozzle.

References Cited by the Examiner UNITED STATES PATENTS Geer 30242 Brarnsen 239-61 Benoit 239-61 Junkins 239-8 H'achmeister 239--61 Brooks 302-42 Kane 23961 Schlemmer 239-61 Carr et a1 239336 M. HENSON, WOOD, JR., Primary Examiner.

EVERETT W. KIRBY, Examiner.

R. S. STROBEL, Assistant Examiner. 

1. A SPRAY APPARATUS FOR FORMING A COMPOSITE SPRAY OF GAS-PROPLLED LIQUID GLOBULES AND SOLID PARTICLES COMPRISING A FIRST NOZZLE, SUPPLY MEANS FOR SUPPLYING A PRESSURIZED GAS TO SAID FIRST NOZZLE, MEANS FOR SUPPLYING A LIQUID TO SAID FIRST NOZZLE IN A MANNER TO EFFECT ATOMIZATION THEREOF AND DISCHARG FROM SAID FIRST NOZZLE IN THE FORM OF A GAS-PROPELLED SPRAY OF FINE-SIZED LIQUID GLOBULES, A SECOND NOZZLE, MEANS FOR SUPPLYING A FINELY-PARTICULATED SOLID POWDER INCLUDING GAS-ACTUATED MEANS FOR FLUIDIZING AND DISCHARGING SAID POWDER AT A CONTROLLED RATE TO SAID SECOND NOZZLE INTO SAID SPRAY FROM SAID FIRST NOZZLE EFFECT ING ENTRAINMENT OF SAID POWDER IN SAID SPRAY, A CONDUIT CONNECTED TO SAID GAS-ACTUATED MEANS AND TO SAID SUPPLY MEANS, AN ORIFICE IN SAID SUPPLY MEANS, SENSING MEANS FOR SENSING THE PRESSURE DROP ACROSS SAID ORIFICE IN RESPONSE TO THE FLOW OF GAS THERETHROUGH TO SAID FIRST NOZZLE, FIRST VALVE MEANS IN SAID CONDUIT OPERATIVELY ASSOCIATED WITH SAID SENSING MEANS AND MOVABLE TO AN OPEN POSITION WHEN A PRESELECTED PRESSURE DROP IS EXCEEDED ENABLING PASSAGE OF GAS TO SAID GAS-ACTUATED MEANS AND MOVABLE TO A CLOSED POSITION PREVENTING PASSAGE OF GAS TO SAID GASACTUATED MEANS WHEN THE PRESSURE DROP IS BELOW THE PRESELECTED LEVEL, AND SECOND VALVE MEANS FOR CONTROLLING THE RATE OF FLOW OF GAS TO SAID FIRST NOZZLE. 